There are a few different ways to find the books you need:
To obtain a dissertation, you can try to borrow it through ILL, but be aware that most institutions do not lend dissertations, or they charge for lending. It is also possible to purchase copies of most dissertations.
If you don't find an appropriate dissertation citation, go to the Information Desk. Any of the librarians can help you do a special database search for dissertations.
See also our Dissertations & Theses page which includes sites with links to fulltext dissertations online.